The measurement of the speed and direction of a gas flow may be performed in a variety of applications. Some of these applications include measuring the speed and direction of wind, measuring the speed of air through a ventilation system, etc.
In a mechanical approach for performing such measurements, a propeller or spinning cups of a cup anemometer may spin in response to a gas flow, and the rotational speed of the propeller or spinning cups may be used to infer the flow speed. To additionally determine wind direction, a wind vane may be employed. Mechanical devices are generally lower cost than other instruments used to determine the speed and direction of a gas flow. However, mechanical devices have moving parts, and are therefore susceptible to the effects of wear and tear, leading to the degradation and eventual failure of the devices.
In an acoustical approach, an ultrasonic anemometer may be used to measure the speed and direction of a gas flow. Sonic pulses may be transmitted between pairs of transducers and the time of flight of the sonic pulses may be used to infer the speed of a gas flow. If three or more transducers are employed, the direction of a gas flow may be also determined. An ultrasonic anemometer provides the advantages of no moving parts, high accuracy, and reliability, while it has the drawbacks of higher power requirements and higher cost.
Devices other than mechanical and acoustical anemometers for measuring the speed and direction of a gas flow are described herein.